Aqueous Delivery System for Low Surface Energy Structures

ABSTRACT

An aqueous delivery system is described including at least one surfactant and at least one water insoluble wetting agent. Further described are low surface energy substrates, such as microporous polytetrafluoroethylene, coated with such an aqueous solution so as to impart a change in at least one surface characteristic compared to the surface characteristics of the uncoated low surface energy substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/138,876 filed May 25, 2005, the entire contents of which areexpressly incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an aqueous system for coating lowsurface energy surfaces and to coated surfaces formed therefrom.

BACKGROUND OF THE INVENTION

Conventional aqueous micellar delivery systems have been usedpredominantly in the pharmaceutical industry to provide both controlleddelivery of drugs and controlled release of pharmaceutical agents. Amicellar solution is one that contains at least one surfactant at aconcentration greater than the critical micelle concentration (“CMC”).In the case of aqueous micellar solutions, when a hydrophobic or lesswater soluble material such as an oil is emulsified in the micellarsolution, an emulsion results. Due to the often high surfactantconcentrations used in many emulsions, the resulting surfactantstabilized emulsion droplets are often very stable. The good stabilityagainst coalescence also makes emulsion droplets ideal carriers forother materials. This technology is typically used in the pharmaceuticalindustry for controlled delivery of pharmaceutical agents such asantibiotics, antimicrobials, antivirals, cardiovascular and renalagents. These agents are commonly incorporated into the hydrophobiccomponent of the carrier emulsion. Frequently, such emulsions arecomprised of a hydrophobic material selected from the group consistingof a long chain carboxylic acid, long chain carboxylic acid ester, longchain carboxylic acid alcohol and mixtures thereof.

A permutation of these aqueous micellar delivery systems aremicroemulsions which form easily, even spontaneously, in the presence oftypically high emulsifier concentrations. Microemulsions areparticularly useful as delivery vehicles because a range of materialscan be contained therein that would otherwise be sensitive to water,such as hydrolysis sensitive materials. In typical pharmaceuticalmicroemulsion applications, the hydrophobic material is a waterinsoluble organic material that is emulsified by surfactants to form adiscontinuous phase in a continuous aqueous phase (see, for example,U.S. Pat. No. 5,952,004 to Rudnic, et, al.). Such microemulsions can beextremely stable and can provide a useful delivery means. For example,pharmaceutical agents may be dispersed into the hydrophobic material anddelivered as part of the aqueous emulsion.

Emulsion technology is also used to create polymeric dispersions whereina monomer is first emulsified in an aqueous surfactant solution and thenpolymerized. The resulting emulsion polymers, commonly referred to aslatexes, have found many uses including paints and coatings. In orderfor a latex to spread across the substrate surface and form a uniformcoating, it is necessary for it to “wet” the substrate to which it isapplied. “Wetting” results when the contact angle, θ, between theaqueous latex and the solid substrate is less than about 90 degrees.Spontaneous wetting occurs when the surface energy between the solid andliquid, γSL is less than the surface energy between the solid and air,γSA. The relationship between these parameters and the liquid-airsurface energy, γLA, is given by the relationship below:

γSL=γSA−γLA*cos(θ)

This relationship is very important when trying to coat a low surfaceenergy substrate (low γSA), such as for example, materials with asurface energy below about 40 dynes/cm, because a very low γSL isrequired.

One low surface energy substrate of particular interest ispolytetrafluoroethylene (“PTFE”) and microporouspolytetrafluoroethylene. Due to the inherent hydrophobicity of PTFE,membranes of these materials are of particular interest when in the formof repellent products such as rainwear. Expanded microporous, liquidwaterproof polytetrafluoroethylene materials, such as those availablefrom W. L. Gore and Associates, Inc., sold under the trademarkGORE-TEX®, as well as expanded PTFE products available from othersuppliers are especially well suited for this purpose. The expanded PTFEmaterials are liquid waterproof, but allow water vapor, in the form ofperspiration, to pass through. Polyurethanes and other polymers havebeen used for this purpose also. To confer good flexibility and lightweight in the materials for use in the textile sector, the microporouslayer should be made as thin as possible. However, a thinner membranewill generally mean a loss of performance, and thin coatings run therisk of decreasing water repellency.

Low surface energy substrates have historically been coated by solutionshaving a low γLA and low contact angle. Suitable coating processes formicroporous low surface energy materials are described in the art, manyof which rely on solvents to wet the desired substrate. For example, EP0581168 (Mitsubishi) describes the use of perfluoroalkyl methacrylatesand perfluoroalkylethyl acrylates for porous polyethylene andpolypropylene membranes. These substances are held in physical contactwith the surface of the polyolefin porous membrane. The fluorinatedmonomer or fluorinated monomer and a crosslinking monomer together witha polymerization initiator are dissolved in a suitable solvent toprepare a solution. For example this solution typically can comprises15% wt. monomer and 85% wt. acetone. After coating, the solvent isvaporized off. The situation is similar with a process for treating thesurfaces of polymers with essentially pure solvent solutions containinglow concentrations (e.g. less than 1.0% wt.) of amorphous fluoropolymers(WO 92/10532). Likewise, solutions of fluorine-containing polymers arealso involved in a patent for coating ePTFE with an amorphous copolymerof tetrafluoroethylene (EP 0561875). In each of these cases, significantquantities of solvent are released during the coating coalescenceprocess. These solvent emissions are both costly and environmentallyundesirable. Moreover, solvent-based wetting systems have the inherentlimitation of incompatability with a broad range of aqueousfluoropolymers, and the concentration of solvent necessary to wet thesubstrate limits the amount and type of additive that can be coated onthat substrate.

Efforts have been made to convert from these solvent based coatingsystems to aqueous coatings systems. However, the challenge of achievingstability of the wetting package and to achieve fast wetting speed arehard to meet. One relatively common approach is to add a water solubleorganic solvent to the aqueous coating solution or latex. U.S. Pat. No,6,228,477 teaches a means to coat a low surface energy, microporous PTFEsubstrate with an otherwise non-wetting, aqueous fluoropolymerdispersion through the use of significant percentages of isopropanol(“IPA”). In one such example, the non-wetting, aqueous fluoropolymerdispersion was diluted to 25% dispersion and 75% IPA, applied to amicroporous PTFE substrate. and the solvent evaporated off to therebyform a uniform coating of the desired fluoropolymer. This processunfortunately requires the use of large amounts of IPA and createssignificant environmental problems. In other examples in this patent, anumber of fluoropolymer treatments were shown to be unstable with highconcentrations of water soluble alcohol, further limiting this IPAwetting system.

Aqueous microemulsion systems have been developed to circumvent the needfor high levels of VOC's in order to wet low surface energy substrates.One such system that does not require the use of IPA or any other VOC'sis taught in U.S. Pat. No. 5,460,872, to Wu et. al. This patent teachesthe use of fluorinated surfactants to lower the surface energy andcontact angle with microporous PTFE as a means to produce a uniformlycoated microporous PTFE substrate. After application of this aqueousdispersion the fluorinated surfactant and the residual water were thenremoved by heating.

High costs of manufacturing and potential environmental issues withthese prior art materials have highlighted the continuing need for asolution to effectively coat low surface energy substrates without highlevels of VOC's or undesirable fluorosurfactants.

SUMMARY OF THE INVENTION

The present invention overcomes the limitation of the prior art byproviding a robust, stable aqueous delivery system. This invention iscapable of wetting low surface energy substrates and thereby can delivera wide range of organic and inorganic materials to form coatingsthereon. The present invention is directed to an aqueous delivery systemof a surfactant and a water insoluble alcohol wetting agent. Optionally,one or more materials that permit greater amounts of wetting agentwithout causing phase separation (i.e., stabilizers) can be added. Addedfunctionality can be incorporated by including one or more additives inthe aqueous delivery system. This invention can be used to deliver arange of functional materials to low surface energy materials,including, but not limited to, functionalized or surface activepolymers. Also described are low surface energy materials, such asmicroporous fluoropolymers, coated by the aqueous delivery system.Additionally, the invention includes a coated article including a lowsurface energy microporous material having a coating on at least aportion of the pore walls of the microporous material, the coatinghaving a measurable amount of surfactant of up to a water insolublealcohol up to 25% by weight based on the total weight of the coatedmicroporous material.

DETAILED DESCRIPTION OF INVENTION

In the present invention, an aqueous solution is produced when at leastone surfactant is used to emulsify at least one water insoluble wettingagent. In a further embodiment, this invention is directed to lowsurface energy substrates, such as microporous polytetrafluoroethylene,coated via such an aqueous solution so as to impart a change in at leastone surface characteristic compared to the surface characteristics ofthe uncoated microporous substrate.

Application to low surface energy substrates relies on good wetting. Toachieve good wetting, the surface tension of the aqueous delivery systemshould to be sufficiently low to penetrate the microporous substrate.For example, a surface tension of less than or equal to about 30dynes/cm is typically required to penetrate expanded microporous PTFE.Higher surface tension wetting systems may accordingly be suitable forhigher energy substrates such as microporous polyethylene or microporouspolypropylene. As previously discussed, the prior art teaches that highlevels of water soluble wetting agents such as isopropanol can be usedto lower γSL in order to enable certain aqueous coating systems to wet amicroporous low surface energy PTFE substrate (U.S. Pat. No,6,676,993B2).

Suitable wetting agents of the present invention include alcohols andmixtures of alcohols that exhibit a low water solubility, such as thosealcohols having five or more carbon atoms in the longest continuouschain, e.g., alcohols with C₅-C₁₀ linear chains, and the like. Forexample, pentanols, hexanols, octanols, and the like, are within therange of suitable wetting agents of the present invention. Further, theaqueous delivery system can incorporate with the water insolublealcohol(s) other water insoluble organics, such as alkanes, etc.Optionally, the wetting agent may also exhibit a low γSL relative to thetargeted low surface energy substrate.

The surfactant(s) of this invention can be a single surfactant or acombination of surfactants. Suitable surfactants are defined as thosethat are able to emulsify the desired wetting agent. For the alcoholsdescribed above, several classes of anionic surfactants can be used,including, but not limited to, those having a structure of R(EO)_(n)OSO₃⁻ or ROSO₃ ⁻ where R can be any organic chain, “O” is oxygen, “S” issulfur, “EO” is ethylene oxide and n=>1. In an alternate embodiment,nonionic surfactants having the structure R(EO)_(n)OH, where n=>1,arealso suitable for this invention, in a preferred embodiment, nonionicsurfactants with a hydrophilic-lipophilic balance (“HLB”) values of tenor greater were found most effective to emulsify the wetting agentsdescribed above. The concentration of surfactant can be adjusted inorder to achieve good emulsification of the desired wetting agent. Forexample, when 4% by weight of hexanol wetting agent (based on the totalaqueous solution weight) is used, a concentration of about 2% of sodiumdodecyl ether sulfate was found to be suitable. In an alternateformulation, 6% wt. of an ethoxylated alcohol was able to emulsify 4%wt, hexanol wetting agent.

In addition to the aqueous delivery system provided by the surfactantand the wetting agent, a stabilizing agent can optionally be added. Astabilizing agent is typically soluble in both the alcohol and water,and it allows a greater amount of alcohol to be stabilized in theaqueous system than without the stabilizer. In one embodiment, glycolswere found to be effective stabilizers, such as but not limited todipropylene glycol (“DPG”), dipropylene glycol monomethyl ether, andpropylene glycol. A wide range of stabilizer concentrations can be useddepending on the amount of additional stability desired. For instance,if a small increase in stability is desired, a small amount of theoptional stabilizer should be used. Conversely, higher stabilizerconcentrations generally further increase the emulsion stability.Exceptions to these general guidelines do however exist. For example,DPG may be an effective stabilizer when used in concentrations rangingfrom less than about 1% wt. up to about 10% wt. based on total aqueousemulsion weight for hexanol-based systems.

In another aspect of this invention, additional functional additives canoptionally be added to the aqueous delivery system. As used herein, theterm “functional additive” is intended to refer to any additionalmaterial which renders further functionality to the low surface energysubstrate than what otherwise exists in the absence of the functionaladditive. Suitable functional additives include materials which havesuitable stability to be delivered and which are either soluble in theaqueous delivery system (either the water or wetting agent) ordispersable in the aqueous delivery system. In one exemplary embodimentof the invention, if the substrate is a polymer layer that is notnaturally oleophobic, it can be rendered oleophobic by incorporatingwithin the aqueous delivery system a functional additive which is anoleophobic material. This unique feature of the invention providessignificant advantages over conventional solvent coating means ofapplying, for example, oleophobic materials. This unique delivery systemof the present invention provides spontaneous wetting of the substrate,and even in the case of microporous substrates, such as described below,which often have tortuous porosity, the present invention can betailored to readily facilitate coating at least a portion of the porewalls of the substrate.

In one embodiment of this invention, suitable low surface energymaterials can include microporous substrates, as noted in the previousparagraph. Suitable microporous polymers can include fluoropolymers,e.g. polytetrafluoroethylene or polyvinylidene fluorides, polyolefins,e.g. polyethylene or polypropylene; polyamides; polyesters; polysulfone,poly(ethersulfone) and combinations thereof, polycarbonate,polyurethanes. Coatings applied via the present invention to suchmicroporous substrates may be designed to either coat the surfaces ofthe microstructure leaving the pores open or it can be designed toeffectively fill a substantial portion of the pores. In instances whereretention of air permeability or high breathability is desired, thepresent invention should be designed to preserve the open microporousstructure, as filling the micropores may destroy or severely lessen thewater-evapor transmitting property of the microporous substrate. Thus,the walls defining the voids in the microporous polymer preferably haveonly a very thin coating of the oleophobic polymer in such anembodiment. Moreover, to maintain flexibility of the substrate, thecoating of the functional material should be sufficiently thin to notimpact the flexibility of the substrate when coated.

Common oleophobic functional additive compositions suitable for thisinvention include oleophobic fluorocarbon compounds. For example, thefluorocarbon can be one that contains perfluoroalkyl groupsCF₃—(CF₂)_(n)—, where n is ≧0. The following compounds or classes ofoleophobic materials, while not exhaustive, can be used:

-   -   Apolar perfluoropolyethers having CF₃ side groups, such as        Fomblin Y—Ausimont; Krytox—DuPont;    -   Mixtures of apolar perfluoroethers with polar monofunctional        perfluoropolyethers PFPE (Fomblin and Galden MF grades available        from Ausimont);    -   Polar water-insoluble PFPE such as, for example, Galden MF with        phosphate, silane, or amide, end groups;    -   Mixtures of apolar PFPE with fluorinated alkyl methacrylates and        fluorinated alkyl acrylate as monomer or in polymer form.        The above-mentioned compounds can also optionally be crosslinked        by, for example, UV radiation in aqueous form solution or        emulsion.

The following polymeric particle solutions, while again not exhaustive,can also be used:

-   -   Microemulsions based on PFPE (see EP 0615779, Fomblin Fe20        microemulsions);    -   Emulsions based on copolymers of siloxanes and perfluoroalkyl-        substituted (meth)acrylates (Hoechst);    -   Emulsions based on perfluorinated or partially fluorinated co-        or terpolymers, one component containing at least        hexafluoropropene or perfluoroalkyl vinyl ether;    -   Emulsions based on perfluoroalkyl-substituted        poly(meth)acrylates and copolymers (products of Asahi Glass,        Hoechst, DuPont and others).    -   Microemulsions based on perfluoroalkyl-substituted        poly(meth)acrylates and copolymers (WU, U.S. Pat. No. 5,539,072;        U.S. Pat. No. 5,460,872);

The concentration of the functional material provided by this inventioncan vary greatly depending on the desired outcome. When an oleophobicfluoropolymer is used as the functional additive material, such as butnot limited to, polymers having —(CF₂)_(n)—CF₃ pendant groups,functional materials of this type can impart very low surface energyvalues to the polymer and thus impart good oil and water resistanceproperties. Representative oleophobic polymers can be made from organicmonomers having pendant perfluoroalkyl groups. These include fluoroalkylacrylates and fluoroalkyl methacrylates having terminal perfluoroalkylgroups of the formula:

wherein n is a cardinal number of 1-21, m is a cardinal number of 1-10,and R is H or CH₃; fluoroalkyl aryl urethanes, fluoroalkyl allylurethanes, fluoroalkyl urethane acrylates; fluoroalkyl acrylamides;fluoroalkyl sulfonamide acrylates and the like. When a low surfaceenergy coating is desired, concentrations from about 1% wt. up to about20% wt, based on total emulsion solids may be effective. When coatingmicroporous substrates, the concentration of the oleophobic functionalmaterial preferably is between about 3% wt. up to about 12% wt. based ontotal emulsion weight.

Alternate embodiments of this invention include other optionalfunctional additive materials. The present invention can be used todeliver particulate functional materials to surfaces, provided that theparticulate can be dispersed in the emulsion wetting system. In someinstances, it may be advantageous to disperse the particulates in adispersing agent which can subsequently be dispersed in the emulsionwetting system. Hence when a substrate is coated with the aqueoussolution, the functional additive particles contained therein will bedeposited onto and/or into substrate and its surfaces in order toeffect, for example, a color change in the case of a pigment, or otherdesirable functional change in the substrate. Carbon particles are ofparticular interest in applications where a change in an electromagneticspectral response or electric or thermal conductivity of the substrateis desired. In applications involving particulates, concentrationsranging from about 0.1% wt. up to about 5% wt. based on total emulsionweight are often appropriate.

The optional functional material of the present invention may also bematerials that are either soluble in the inventive aqueous deliverysystem or dispersible in the inventive aqueous delivery system. The listof soluble materials that can be used in conjunction with the presentinvention include but are not limited to simple salts (e.g., AgNo3,CuSo4), simple compounds, polyacrylic acid, polyacrylamide, melamine,polyvinyl alcohol, salts, and dyes. The list of dispersible materialsthat can be used in conjunction with the present invention include butare not limited to polyfluoroacrylates, polystyrene, pigments, carbonblack, and aluminum oxide. One requirement for these dispersiblematerials is that the particle size be sufficiently small so that thencan physically enter the pores of the microporous substrate to whichthey are being applied. When the microporous substrate is inherentlyhydrophobic, such a coating can change the surface characteristic fromhydrophobic to hydrophilic.

Other useful permutations of this invention are also encompassed withinthe breadth of functional materials that can be stable in the presentaqueous delivery system and thereby subsequently applied to a range ofmicroporous and nonmicroporous substrates.

Definitions

For the purposes of this application the following terms shall berecognized to have the meaning set forth below unless otherwiseindicated:

“Air permeable” means that airflow is observed as determined by theGurley test described below. It will be appreciated by one of skill inthe art that an air permeable material will also be moisture vaporpermeable.

“Air-impermeable” means that no airflow is observed for at least twominutes as determined by the Gurley test described below.

“Hydrophilic” material denotes a porous material whose pores becomefilled with liquid water when subjected to liquid water without theapplication of pressure.

“Microporous” term is used to denote a continuous layer of materialcomprised of interconnecting pores which create a passageway extendingfrom one surface of the layer to the opposite surface of the layer.

“Oleophobic” means a material that has an oil resistance of 1 or more,as measured by the Oil Repellency Test, below.

Test Procedures

Air Permeability/Impermeability—Gurley Number Test

Gurley numbers were obtained as follows:

The resistance of samples to air flow was measured by a Gurleydensometer (ASTM) D726-58) manufactured by W. & L. E. Gurley & Sons, Theresults are reported in terms of Gurley Number, which is the time inseconds for 100 cubic centimeters of air to pass through 6.54 cm. sup.2of a test sample at a pressure drop of 1.215 kN/m² of water. A materialis air-impermeable if no air passage is observed over a 120 secondinterval.

Oil Repellency Test

In these tests, oil rating was measured using the AATCC Test Method118-1983 when testing film composites. The oil rating of a filmcomposite is the lower of the two ratings obtained when testing the twosides of the composite. The higher the number, the better the oilrepellency. A value of greater than 1, preferably 2 or more, morepreferably 4 or more, is preferred.

The test is modified as follows when testing laminates of the filmcomposite with a textile. Three drops of the test oil are placed on thetextile surface. A glass plate is placed directly on top of the oildrops. After 3 minutes, the reverse side of the laminate is inspectedfor a change in appearance indicating penetration or staining by thetest oil. The oil rating of the laminate corresponds to the highestnumber oil that does not wet through the laminate or cause visiblestaining from the reverse side of oil exposure. The higher the number,the better the oil repellency. A value of greater than 1, preferably 2or more, more preferably 4 or more, and most preferably, 6 or more, ispreferred.

EXAMPLES Example 1

In order to determine the amount of 1-hexanol needed to wet ePTFE with anon-ionic surfactant, a nonionic surfactant, Iconol DA-6 (BASF,ethoxylated alcohol, HLB 13), was added to de-ionized water to make a 4weight % solution. 1-Hexanol was added incrementally to the Iconol DA-6solution. After each addition of 1-hexanol, the stability of the mixturewas examined for phase separation.

The ability of this mixture to wet and penetrate a 50 g/m2 ePTFEmembrane (0.2 micron pore size, 100 micron thickness, Gurley number ofabout 25 sec., W. L. Gore and Associates, Inc, Elkton, Md.) was assessedby measuring the time required for a drop to clarify fully the membrane.The data are shown in Table I. Pure 1-hexanol wets ePTFE in 1-2 sec.Surprisingly, a dilute hexanol (1.7%) and surfactant blend wets ePTFE asfast as pure hexanol.

TABLE I Weight % Time to Clarify 1-Hexanol ePTFE (sec) Stability 0 >30stable, 1 phase 1.2 4 stable, 1 phase 1.7 1-2 stable, 1 phase

Example 2

Witcolate ES-2 (30% solids, dodecyl ether sulfate, obtained from WitcoChemicals/Crompton Corporation, Middlebury, Conn.) was used to determinethat a level as high as approximately 11% surfactant solids could beused to wet ePTFE (50 g/m2) in combination with 1-hexanol. A mixture of3.9 g of Witcolate ES-2 and 6.1 g of de-ionized water was prepared.1-Hexanol was added incrementally to this mixture, and the stability andwetting time for ePTFE was measured as in Example 1. The data are shownin Table II.

TABLE II Witcolate ES-2 Time to Clarify (Wt % solids) 1-Hexanol (Wt %)ePTFE (sec) Stability 12 0 >30 stable, 1 phase 12 1.4 >30 stable, 1phase 11 3.7 >30 stable, 1 phase 11 5.9 partial in 30 sec stable, 1phase 11 7.6 7 stable, 1 phase 11 8.5 >30 stable, 1 phase

Example 3

In order to determine the upper range of 1-hexanol (approximately 30weight %) that could be used to wet ePTFE, 1.3 g of Witcolate ES-2 (30%solids, dodecyl ether sulfate, obtained from Witco Chemicals/CromptonCorporation, Middlebury, Conn.) was added to 8.7 g of de-ionized water.1-Hexanol was added incrementally to this mixture, and the stability andwetting time for ePTFE was measured as in Example 1. The data are shownin Table III.

TABLE III Witcolate ES-2 Time to Clarify (Wt % solids) 1-Hexanol (Wt %)ePTFE (sec) Stability 4 0 >30 stable, 1 phase 3 13 2 stable, 1 phase 317 2 stable, 1 phase 3 21 3 stable, 1 phase 3 25 2 stable, 1 phase 3 3110 stable, 1 phase

Example 4

In addition to nonionic and anionic surfactants, cationic surfactantswere determined to be useful in combination with 1-hexanol to wetquickly ePTFE, as follows. A dodecyldimethylethyl quaternary ammoniumbromide, DAB, (0.3 g) was added to 9.7 g of dc-ionized water. 1-Hexanolwas added incrementally to this mixture, and the stability and wettingtime for ePTFE was measured as in Example 1. The data are shown in TableIV.

TABLE IV DAB 1-Hexanol Time to Clarify (weight %) (Weight %) ePTFE (sec)Stability 3 0 >30 stable, 1 phase 3 1.3 >30 stable, 1 phase 3 2.7 13stable, 1 phase 3 4.2 2 stable, 1 phase

Example 5

To determine that compounds soluble in both the water-insoluble alcoholand water such as dipropylene glycol (DPG) can be used to increase thestability of the wetting mixture, a mixture (4 weight %) of a nonionicethoxylated alcohol surfactant (Iconol TDA-9 from BASF) was prepared.Without DPG, 1-hexanal would cause phase separation at 2.5% 1-hexanol.The addition of 4 weight % DPG increased the stability and the abilityto wet ePTFE (50 g/m2). The data are shown in Table V.

TABLE V Time to Clarify Iconol TDA-9 1-Hexanol DPG ePTFE (Wt. %) (Wt. %)(Wt %) (sec) Stability 4 0 4 >30 stable, 1 phase 4 0 4 15 stable, 1phase 4 2.1 4 12 stable, 1 phase 4 2.9 4 7 stable, 1 phase 4 3.6 4 <1stable, 1 phase

Example 6

Other water-insoluble alcohols were also examined. Pure 1-octanolclarifies ePTFE (50 g/m2) in 5 seconds. A dilute mixture of 1-octanolwith Witcolate ES-2 (30% solids, dodecyl ether sulfate, obtained fromWitco Chemicals/Crompton Corporation, Middlebury, Conn.) can wet ePTFEas fast as pure octanol. A 13 weight percent (4 weight % solids)Witcolate ES-2 solution was prepared. 1-Octanol was added incrementallyto this mixture. The stability and wetting time for ePTFE was measuredas in Example 1. The data are shown in Table VI.

TABLE VI Witcolate ES-2 Time to Clarify (Wt % solids) 1-Octanol (Wt %)ePTFE (sec) Stability 4 0 >30 stable, 1 phase 4 1.4 >30 stable, 1 phase4 2.9 21 stable, 1 phase 4 3.9 11 stable, 1 phase 4 4.9 7 stable, 1phase 4 6.2 5 stable, 1 phase 4 7.3 4 stable, 1 phase

Example 7

The ability of surfactant and hexanol mixtures to wet and coat ePTFEwith oleophobic materials was examined. Mixtures of 13 weight percent (4weight percent solids) Witcolate ES-2 (30% solids, dodecyl ethersulfate, obtained from Witco Chemicals/Crompton Corporation, Middlebury,Conn.) and approximately 6 weight percent 1-hexanol were prepared withvarious fluoroacrylate polymers (9 weight percent solids). The followingfluoropolymers were used: AG415 and AG4210 (Asahi Glass Company), Zonyl7040 (DuPont), and TG-532 (Daikan). These mixtures were spread on onesurface of an expanded PTFE membrane (about 20 g/m2, thickness of about40 micron, and Gurley number of about 15 sec.) until the membrane wasclarified. The coated ePTFE was placed in a solvent oven at 190° C. for2.5 min. The time for a drop of these coating mixtures to clarify ePTFE(50 g/m2) was measured. The stability of the mixture was examined. Oilratings on the coated and uncoated side of the ePTFE (20 g/m2) weremeasured. Additionally, the air permeability was determined by measuringthe time for 100 cm3 of air to flow through the coated membrane(Gurley). The data show that a range of fluoropolymers can be used tocoat ePTFE (Table VII). The uncoated ePTFE has a Gurley of 15.7 sec. Theoil rating of ePTFE (uncoated) was 1.

TABLE VII Witcolate Time to Oil Rating ES-2 1- Wet (coated/ (wt. %Hexanol Fluoropolymer ePTFE uncoated Gurley solids) (wt %) Type/(wt %solids) (sec) side) (sec) 3.9 6.1 AG415/9 wt % 2 8/6 62.9 3.9 6.3 Zonyl7040/9 wt % 2 7/6 57.3 3.9 6.1 TG532/9 wt % 1 8/8 38.1 3.9 5.0 AG4210/9wt % 8/7 38.7

Example 8

Multiple functional additives were used to coat an expanded PTFEmembrane (20 g/m2, W. L. Gore and Associates, Inc.). A mixture of 1.3 gof Witcolate ES-2 (30% solids, dodecyl ether sulfate, obtained fromWitco Chemicals/Crompton Corporation, Middlebury, Conn.), 0.6 g of1-hexanol, 6.4 g of de-ionized water, 1.5 g of AG8025 (Asahi GlassCompany), 0.2 g of melamine resin (Aerotex 3730 from Cytec), and 0.02 gof catalyst (zinc nitrate) was prepared. This mixture wetted theexpanded PTFE immediately. The coated ePTFE was placed in a solvent ovenat 190° C. for 3 min. The air permeabilit_(y) of the cured sample wasmeasured (Gurley of 48.7 sec for 100 cm3). The sample was alsodetermined to be oleophobic (oil rating of 8 on the coated side and 6 onthe uncoated side).

Example 9

In this example, a 5 mil thick, high molecular weight microporouspolyethylene (Dewal Corporation) was rendered oleophobic and airpermeable using surfactant and hexanol blends with fluoropolymers inaccordance with the present invention. Specifically, a mixture of 1.3 gof Witcolate ES-2 (30% solids, dodecyl ether sulfate, obtained fromWitco Chemicals/Crompton Corporation, Middlebury, Conn.), 0.6 g1-hexanol, 5.1 g de-ionized water, and 3.0 g of AG8025 (Asahi GlassCompany) was prepared. This mixture was observed to wet the microporouspolyethylene membrane. The coated membrane was heated at 190° C. for 2min. The oleophobicity of the coated and uncoated sides was measured andwas determined to be an oil rating of 7 for each side. A sample of theuncoated precursor polyethylene membrane had an oil rating of lessthan 1. The air permeability was also measured for the coated sample andthe uncoated precursor. The coated sample had a Gurley (100 cm3)measurement of 1.5 sec. The uncoated precursor polyethylene microporousmembrane had a Gurley (100 cm3) of 0.3 sec.

1. An aqueous mixture comprising at least one water insoluble alcoholand at least one surfactant.
 2. The aqueous mixture of claim 1, whereinsaid at least one water insoluble alcohol comprises a C₅-C₁₀ linearbackbone.
 3. The aqueous mixture of claim 1, wherein said at least onewater insoluble alcohol is present in an amount of up to about 30% byweight of the aqueous mixture.
 4. The aqueous mixture of claim 1,wherein said at least one water insoluble alcohol is present in anamount of up to about 8% by weight of the aqueous mixture.
 5. Theaqueous mixture of claim 1, wherein said at least one surfactant ispresent in an amount of up to about 15% by weight of the aqueousmixture.
 6. The aqueous mixture of claim 1, further comprising at leastone additive.
 7. The aqueous mixture of claim 1, further comprising atleast one stabilizing agent.
 8. The aqueous mixture of claim 6, whereinsaid at least one additive is soluble in the aqueous mixture.
 9. Theaqueous mixture of claim 6, wherein said at least one additive isdispersible in the aqueous mixture.
 10. The aqueous mixture of claim 8,wherein said at least one additive comprises least one simple salt. 11.The aqueous mixture of claim 10, wherein said at least one additivecomprises silver nitrate.
 12. The aqueous mixture of claim 10, whereinsaid at least one additive comprises copper sulfate.
 13. The aqueousmixture of claim 8, wherein said at least one additive comprises atleast one polymer soluble in the aqueous mixture.
 14. The aqueousmixture of claim 13, wherein said at least one polymer comprisespolyacrylic acid.
 15. The aqueous mixture of claim 13, wherein said atleast one polymer comprises sodium polyacrylic acid.
 16. The aqueousmixture of claim 13, wherein said at least, one polymer iscrosslinkable.
 17. The aqueous mixture of claim 13, wherein said atleast one polymer comprises polyelectrolyte.
 18. The aqueous mixtureclaim 16, wherein said at least one polymer comprises polyelectrolyte.19. The aqueous mixture of claim 8, wherein said at least one additivecomprises at least one melamine.
 20. The aqueous mixture al claim 8,wherein said at least one additive is polymerizable.
 21. The aqueousmixture of claim 9, wherein said at least one additive comprises carbon.22. The aqueous mixture of claim 9, wherein said at least one additivecomprises at least one polymer.
 23. The aqueous mixture of claim 22,wherein said at least one polymer is cross-linkable.
 24. An aqueousmixture comprising a) at least one water-insoluble alcohol with a C₅-C₈linear backbone in an amount up to about 15% by weight of the aqueousmixture; and b) at least one surfactant, wherein said aqueous mixturewets a low surface energy microporous substrate in 10 seconds or less.25. An aqueous mixture comprising a) hexanol in an amount of up to about30% by weight of the aqueous mixture; and b) an ethoxylated alcohol witha hydrophobic/lipophobic balance of 10 or greater,
 26. An aqueousmixture comprising a) hexanol in an amount of up to about 30% by weightof the aqueous mixture; and b) an ethoxylated sulfate alcohol.
 27. Theaqueous mixture of claim 26, wherein said ethoxylated sulfate alcoholhas 0-3 mol of ethoxylation.
 28. An aqueous mixture comprising a)hexanol in an amount of up to about 30% by weight of the aqueousmixture; and b) an arylalkyl sulfonate.
 29. An aqueous mixturecomprising a) hexanol in an amount of up to about 30% by weight of theaqueous mixture: and b) a quaternary ammonium salt with a C₆-C ₁₈ carbonatom content per molecule.
 30. An aqueous mixture comprising a) hexanolin an amount of up to about 30% by weight of the aqueous mixture: and b)an an alkylnapthalene sulfonate.
 31. An aqueous mixture comprising a)hexanol in an amount of up to about 30% by weight of the aqueousmixture; and b) a diol with a C₆-C₂₀ carbon atom content per molecule.32.-37. (canceled)